1. Field of the Invention
The present invention relates to an inspection system for work boards (boards to be worked) such as building boards, and in particular, to an inspection system for identifying work boards and automatically inspecting the surface of work boards that have been treated in each manufacturing process.
2. Description of the Related Arts
In a conventional continuous work line handling work boards, for instance, the shape and color tone of a semi-finished product are frequently caused to change on every occasions after finishing each manufacturing process. For example, in a continuous coating line of building boards, the color tone of the building board is caused to apparently change upon finishing each manufacturing process even if the original shape of the building board or work board is not changed.
As mentioned above, the external appearance of semi-finished product to be shown after finishing each manufacturing process in a continuous work line is frequently caused to change more or less as compared with the external appearance of the same semi-finished product obtained in the previous manufacturing processes.
In such cases, instead of performing an inspection of individual building boards at each manufacturing process thereof, an inspection process is usually performed at the final stage of manufacturing process so as to perform the inspection on the finally finished product. The building board that has passed through this inspection is then usually marked with a specific manufacturer's serial number so as to make it possible to distinguish each building board by this serial number. The reason for performing the inspection at the final stage of manufacturing process may be attribute to the fact that it is very difficult to uniformly impose inspection conditions at a point midway through the manufacturing process. For example, the object of inspection may not be moving along a fixed location of transferring line, or the object of inspection just transferred from a drying process may inevitably undergo a physical or chemical change due to a thermal change with time. Namely, the fact that the object of inspection is not necessarily in a stable state at the midway point of the manufacturing process is one reasons for not performing the inspection at the midway point.
However, if an unexpected inappropriate coating treatment is happened to be performed in a continuous coating line to thereby generate a non-uniformity of coating, an inappropriately coated semi-finished products will be unavoidably subjected to the next working process since it is impossible to find out such an accident unless the coated state is always watched. As a result, it will bring about a serious problem that defective building boards will be continuously produced in large quantities.
Even so, it may be severe to entrust an operator with such a watching operation, and moreover, such an idea is undesirable in promoting the labor saving.
On the other hand, a line monitoring system using a television camera is widely adopted in a manufacturing plant. However, most of them are employed for the purpose of watching if there is any abnormal moving of work boards. Namely, there is no case wherein the line monitoring system is employed for the purpose of inspecting any change in the external appearance or color tone of work boards at each manufacturing process.
Of course, there is a case wherein a monitoring system is employed for watching various controlling items such as temperature, humidity and pressure at each manufacturing process. However, as far as the inspection and evaluation of semi-finished product obtained from each process are concerned, it is inevitable at present to rely on the operator's naked eyes.
Meanwhile, when any defect is found on a finished product and the cause thereof is attempted to trace, the manufacturing plant as well as the produced date of the defective product can be identified from the specific manufacturer's serial number thereof. However, it would be impossible to trace the specific manufacturing conditions under which the product is produced at each manufacturing process, so that it would be impossible to trace the fundamental cause for the production of the defective product.